The present invention relates to a material composition, comprising on the one hand a particulate or granular material and, on the other hand, a binder which is disposed as a coating on the particles or the grains, the binder comprising a hydroxyl-terminated polymer cross-linked by a boron compound.
The present invention also relates to a method of producing a material composition, comprising the steps that a quantity of particles or grains is placed in a mixer; that at least one first ingredient included in the binder comprising a hydroxy-terminated polymer of low viscosity is supplied to the mixer; and that a second ingredient in the form of a cross-linking agent containing boron is supplied to the mixer.
Numerous model clays or similar kneadable materials are previously known in the art and are employed both for artistic purposes and also by children at play. It is a known fact that many of these materials require a certain working and gentle heating in order to obtain the desired plasticity and mouldability.
In order to be able to use the mouldable or formable matrix so as to make figures in moulds, it is necessary that the matrix releases or slips readily from the materials from which the moulds are made. The adhesive capacity of matrix or composition to its surroundings must therefore be limited, which also entails the effect that the matrix is, at the same time, perceived as less tacky and easy to handle.
Another problem which is relevant when the clay or the composition is handled by small children, in particular in the event of repeated use, is that bacteria and other contaminants may grow in the handled composition, which is unsuitable not least when the composition is handled in large children's groups, such as in the child care services. At the same time, the consistency of the modelling clay or the composition is reduced in that liquid, for example in the form of sweat or saliva, is absorbed by the composition.
One example of a material known in the art is so-called trick dough which consists mostly of flour, water and salt. Another similar material which includes further additives is marketed under the trademark Play-Doh®. These materials dry out when the water evaporates during use. In addition, the material does not slip or release from deep moulds of plastic or similar materials.
In order to obtain an interesting structure which is readily mouldable, it is possible to cause a relatively large proportion of particles to be included in the material which will then have a granular structure which, for example, may be likened to wet sand. Moreover, the total volume of the kneadable material increases at the same time, at least by the volume of the particles included.
One example of a prior art material which satisfies the above-outlined criteria at least as regards workability, reasonably low tackiness and the desired granular structure as a result of the particles included is the Applicant's own Application under serial number SE 0500663-0. However, this material has, in addition, specific properties in that it may be baked in an oven in order to produce hard figures that are moreover water-resistant. If a soft material is once again desired, the hard figures are heated up, whereafter the composition must be kneaded during cooling in order to become soft at room temperature. This latter working takes up a not inconsiderable amount of time and effort, which could be a drawback in certain circumstances, for example in the child care services where there is occasionally a shortage of personnel. A certain adhesion of the binder of the material occurs to normal plastics which are included in moulds and equipment, which may also be perceived as a drawback.
Another prior art material is described in U.S. Pat. No. 5,607,993 which discloses a so-called “bounce clay”. In working, this material lacks a manifest particulate structure, nor is it immediately intended for figure moulding, but rather for use where its bouncing properties are appreciated. The bouncing clay contains a small proportion of particles which merely function as a filler with a view to imparting lower density to the bouncing clay. The particles are extremely small and are completely surrounded by the silicone material and their granular structure cannot therefore be sensed on handling of the composition. The “bouncing clay” is available in many different variations, and the chemical compositions are well-known as well as their effects on the properties of the material.
There is hence a need in the art to realise a composition principally for play and educational purposes where the property that the composition is readily mouldable and formable is combined with a low level of adhesion to its surroundings and an attractive and pleasant structure, but which is different from the materials already existing in the art.
According to an aspect of the present invention, the material composition intimated by way of introduction is characterised in that the concentration of the particulate or granular material is about 90-98 vol % of the finished composition.
According to another aspect of the present invention, in a method for producing the material composition, the first ingredient included in the binder is distributed as thin layers on the surfaces of the particles or grains, and that thereafter the cross-linking agent in dissolved form is supplied to the mixer for cross-linking the thin layers of the first ingredient.